The invention relates to foamed or surfactant fluid systems (VES's) that are applied in various applications of the oil industry, providing a degree of biodegradability, and meeting the requirements of Alberta Energy and Utilities Board Directive 27, in that they pass a test of their toxicity to light emitting bacteria.
New Alberta Energy and Utilities Board Directive 27 requirements (that require following Alberta Energy and Utilities Board Guide 50 “Drilling Waste Management”) put restrictions on the use of oilfield fluids in wells, such as those penetrating shallow gas reservoirs, where the potential exists for fluids to contaminate fresh-water aquifers and water wells, if hydraulic communication is inadvertently established. The Directive requires that any fluid pumped must pass the bacterium toxicity test protocol of Guide 50, similar to that used for qualifying drilling and other fluids for land surface disposal. In this test, bioluminescent bacteria are added to the as-pumped fluid. The sample is aged for a limited amount of time, and the inhibition of the natural bioluminescence of the sample is measured. If the EC50 is >75%, the fluid passes; otherwise it fails. EC50 is the relative sample concentration (in dilution water) required to decrease light output by 50%. A sample with a value of EC50 of 10% means that a sample concentration of 10% in dilution water lowers the light output of the microorganisms by 50%. Most hydraulic fracturing fluids that are viscosified with viscoelastic surfactants, or that contain foamers and/or other additives, for example fracture fluids used in friction-reduced water (slickwater) treatments (using high fracture volumes, pump rates, and pressures) can not pass this test. This test is well known to those of skill in the art. It uses Microtox® reagents (supplied by AZUR Environmental, Carlsbad, Calif., U.S.A.) which are the freeze dried (lyophilized) luminescent bacterium Photobacterium phosphoreum (marine water organisms, strain NRRL B-11177).